A system for radio-reporting information of the current position of a vehicle and information about the occurrence of illegal use of the vehicle from the vehicle to an owner of the vehicle or a police station, when the vehicle being illegally used is detected, is well known. See Japanese Patent Publication Application No. H09-249095, for example. Furthermore, a system for radio-reporting information about the occurrence of vehicle theft from a vehicle to an owner of the vehicle, when the vehicle being stolen is detected, is also well known. See Japanese Utility Model Registration Publication Application No. H05-49524, for example. According to the above-mentioned conventional systems, when the illegal activity regarding the vehicle such as the theft of the vehicle is detected, the detected information is reported to an opponent to be reported to by radio. Therefore, even if the owner of the vehicle is separated from the vehicle, the owner can be remotely notified about the illegal activity regarding the vehicle and thereby it is possible to attempt to prevent such an illegal activity.
However, in the above-mentioned systems where the report is sent from the vehicle to the opponent to be reported to by the radio communication, if a radio wave obstructing (interfering with) the receipt of the radio report is generated near the vehicle, it is difficult for the information sent from the vehicle to the opponent to be reported to, to be received. Hence, in a case where the illegal activity such as the theft is done to the vehicle, even if the illegal activity is detected, it may not be possible for the opponent to receive the radio report from the vehicle. In the system where the illegal activity affecting the vehicle is remotely reported to the owner of the vehicle, if the obstruction radio wave that obstructs receipt of the radio report is not avoidable, the reliability of the system is decreased.